In conventional cameras, during determination of the state of charge of the battery, it is necessary to cover the photoelectric cell by hand during actuation of a switch or key to note whether a warning or control lamp lights up when the photoelectric element is screened off. When the test is carried out properly, activation of the control lamp to its normal level of intensity indicates that the battery is at a satisfactory state of charge, i.e. at a satisfactory voltage. The difficulty with this type of arrangement is that an inexperienced camera user may on occasion forget to screen off the photoelectric cell when actuating the switch or key, or may screen off the photoelectric element only incompletely. A test result obtained under such conditions may lead to unnecessary, premature replacement of the battery.
As is evident, then, it would be desirable that the camera be so constructed that the photosensitive element be automatically screened off whenever the battery test switch or key is actuated. In other words, the actuation of a single testing key should be sufficient for achieving the desired test result without any additional manipulation.